Vehicle tire air pressure monitoring system

ABSTRACT

A monitoring electrical circuit includes either a pressure gauge or signal light on the dashboard of an automobile for each of the tires on the vehicle and the circuit includes a pressure responsive switch on each of the wheels. The electrical circuit in each of the front wheels includes a terminal on the outer end of the front axle frictionally engaged by an electrically conductive spring held in and insulated from an enclosure cover rotatable with the front wheel. The electrical circuit through the rear wheels involves a conductive ring on the axle at each wheel engaged at its periphery by a carbon brush held stationary on the axle housing. The air pressure signalling units on the wheels are positioned parallel to the axis of rotation of the wheels such that they are unaffected by the centrifugal forces generated by the wheels when turning.

United States Patent Drown I July 4, I972 [72] Inventor:

[73] Assignee:

George C. Drown, Fort Dodge, Iowa Leward M. Larson, Fort Dodge, Iowa: apart interest [22] Filed: Aug. 25, I970 [21] Appl.N0.: 66,690

Cescati ..34()/58 X Beavers et al i 340/58 X Primary Examiner-Alvin H.Waring Attorney-Zarley, McKee & Thomte [57] ABSTRACT A monitoringelectrical circuit includes either a pressure gauge or signal light onthe dashboard of an automobile for each of the tires on the vehicle andthe circuit includes a pressure responsive switch on each of the wheels.The electrical circuit in each of the front wheels includes a terminalon the outer end of the front axle frictionally engaged by anelectrically conductive spring held in and insulated from an enclosurecover rotatable with the front wheel. The electrical circuit through therear wheels involves a conductive ring on the axle at each wheel engagedat its periphery by a carbon brush held stationary on the axle housing.The air pressure signalling units on the wheels are positioned parallelto the axis of rotation of the wheels such that they are unaffected bythe centrifugal forces generated by the wheels when turning.

10 Claims, 7 Drawing Figures Patented July 4, 1972 firraewa j VEHICLETIRE AIR PRESSURE MONITORING SYSTEM The cause of many highway accidentscan be traced to improperly inflated tires. The manual checking of thetire inflation pressure is time consuming and too infrequentlyperformed. The loss of tire pressure while the vehicle is moving willusually go undetected until after it is too late. The tire pressuremonitoring system of this invention will provide either continuousmonitoring of the tire pressure for each tire as accurately as desiredor will actuate signalling lights when a dangerously low predeterminedair pressure has been reached by any of the tires.

One of the difficult problems in monitoring the pressure of vehicletires is in establishing a reliable electrical circuit through therotating wheels. The monitoring circuit of this invention involves afoolproof electrical circuit for botlt the front and rear wheels whichwill not only be reliable for transmitting air pressure information itwill also indicate for both of the front and rear wheels the presence ofdefective wheel bearings by grounding the circuit at the front and rearaxles and thereby turning on the associated warning light.

The signalling units on the wheels are so positioned parallel to theaxis of rotation for the wheels that the centrifugal forces developed asthe wheels rotate do not affect the signalling unit sensitivity.

This invention consists in the construction, arrangements andcombination of the various parts of the device, whereby the objectscontemplated are attained as hereinafter more fully set forth,specifically pointed out in the claims, and illustrated in theaccompanying drawings in which:

FIG. 1 is a cross-sectional view of a front wheel illustrating theassociated air pressure signalling unit and electrical circuitry;

FIG. 2 is an enlarged fragmentary cross-sectional view of the frontwheel axle and enclosure rotatable with the wheel;

FIG. 3 is a cross-sectional view similar to FIG. 1 but showing the rearwheel construction;

FIG. 4 is an enlarged fragmentary view of the rear wheel construction;

Fig. 5 is enlarged cross-sectional fragmentary view of the pressuresignalling unit mounted horizontally in a wheel;

FIG. 6 is an electrical schematic drawing of the electrical monitoringsystem circuitry; and

FIG. 7 is an alternate embodiment of the electrical circuitry showing apressure signalling gauge.

The vehicle tire pressure monitoring system of this invention isreferred to generally in FIG. 6 by reference numeral 10 and includessignal lights 12, 14 and 16 for the front, rear and spare tiresrespectively. A air pressure signalling unit 18 is provided on each ofthe wheels and makes an electrical circuit through front and rear wheelbrush units 20 and 22, respectively.

The front wheel structure is best seen in FIGS. 1 and 2 and includes abrake drum 24 having a brake shoe 26. A brake drum 24 is secured bybolts 28 to the front wheel 30 on which a tire 32 is mounted. The wheelspindle 34 is provided with bearings 36 in a wheel hub 38 secured to thebrake drum 24. A dust or grease cap or enclosure cover 40 is threadablysecured to the hub to enclose the outer end of the spindle 34 and thewheel bearings held in place by an adjusting nut 42.

A bore or passageway 44 extends through the spindle and an insulatedconducter wire 46 extends therethrough and terminates in a button 48seated in an insulator 50 on the axial center of the spindle 34. A bead52 is provided directly on the axial center of the button 48 and isadapted to engage a bead 54 at the apex of a conically shaped coilspring 56 seated in the grease or dust cover 40 and insulated by aninsulator 58. An insulated conductor wire 60 extends through a grommet62 in the enclosure cover 40 and is connected to the spring 56 therebymaking electrical contact between the rotating wire 60 on the wheel 30and the stationary wire 46 in the spindle 34. When the front wheel isproperly assembled with nondefecu've wheel bearings 36 the spring 56will maintain yieldable frictional contact between the bead 54 thereonand the head 52 on the button 48 in the outer end of the spindle 34.Upon looseness developing in the front wheel due to bearing wear thebead 54 on the spring 56 will slip over out of axial alignment with thebead 52 and contact the spindle 34 thereby grounding the circuit throughthe corresponding signal light 12.

The signalling unit 18 mounted in the wheel 30 is shimmed by the beveledoppositely disposed mounting shims 70 and 72 on the annularly disposedwheel flange 74 such that the signalling unit 18 is horizontallyoriented to eliminate any affect thereon due to centrifugal forcesdeveloped during the rotation of the wheel. An adjustment nut 76 on theinside of the air chamber 78 holds the signalling unit 18 in place. Apassageway 78 is provided through a sleeve 80 in communication with adiaphragm 82 against which a spring 84 bears. The spring 84 is held inplace by a cover 86. A switch element 88 is yieldably held in an openposition as seen in FIG. 5 by the air pressure on the diaphragm 82 whichalso bears against a pin 90 connected to the switch element 88. Upon theair pressure against the diaphragm 82 being reduced the pin 90 andswitch element 88 will move to the left as seen in FlG. 5 and the switchelement 88 will bear against the terminal 94 connected to the insulatedwire 60 thereby completing the circuit through the associated signallight 12.

The air pressure signalling unit 18 will imbalance the front wheel 32and thus a counterbalance weight is provided diametrically opposite onthe wheel flange 74.

A rear tire 102 is shown in FIG. 3 mounted on a wheel 104 secured bybolts 106 to the flange 108 of the rear drive axle shaft 110. A brakedrum 112 is also secured on the shaft flange 108 and includes a brakeshoe 114 enclosed in the brake drum adjacent to a back plate 1 16. Theaxle shaft I I0 is mounted in wheel bearings "8 held in place by anouter hearing retainer 120.

An arm 122 is secured to the outer retainer in turn stationary andsecured to the back plate 116 on the axle shaft housing 123. A carbonbrush 124 is biased by a spring 126 in a brush holder toward a conductorring element 128 mounted on the axle shaft 110 and insulated by a ringelement 130. An insulated wire 132 extends through a grommet 134 in theback plate 116 and is operatively connected to the associated signallight 14. Similarly, an insulated wire extends from the conductor ring128 and through an opening 144 in the shaft flange 108 and thencethrough the break shoe 112 and the wheel 104 to where it is connected toa terminal 142 in the air pressure signalling unit 18 hereinbeforedescribed with reference to the front wheel 30. Defective rear wheelhearings will cause brush holder 125 on the arm 122 to be grounded outagainst the ring 128 and thereby activate the associated signal light.

The vehicle air pressure monitoring system circuitry a illustrated inFIG. 6 also includes a testing circuitry to check the signal lights l2,l4 and 16 such that when the ignition switch is moved to the startposition a circuit through the starter 152 and the lights l2, l4 and 16is closed by the ralay I51. Accordingly, at this time if the lights areoperative they should light. Upon return of the ignition key to the onposition the lights should go out and only again be relit upon one ofthe tires being deflated to a predetermined pressure which would causethe pressure signalling units 18 to close the electrical circuit. ln thecase of either a front or rear wheel bearing becoming defective thecircuit will be grounded and closed thereby lighting the signal lights.Each of the lights l2, l4 and 16 include a switch operated with theignition switch 150 such that when the ignition switch 150 is in thedash line off position the signal lights will be inoperative and therebyavoid running the vehicle battery down.

. An alternate circuit I80 is shown in FIG. 7 which will enable precisereadings in pounds to be registered on a signalling indicator 14Aconnected through the switch 160 and the switches 20 or 22 for the frontand rear wheels respectively to the air pressure signalling unit 18A.The air pressure signalling unit 18A includes a sleeve 80 exposed to theair pressure of the tire and pressing against a diaphragm 82 againstwhich a spring 84A bears. The spring 84A is held in place by anenclosure cover 86A. A resistance element 182 is engaged by a movableterminal 184 carried on the diaphragm 82 such that the voltage dropacross the pressure signalling unit 18A will vary with the amount ofresistance put into the circuit as a result of the air pressure in thetire. The greater the air pressure in the tire the less the resistancein the circuit will be and accordingly the gauge 14A will register ahigher pressure. Conversely, as the pressure in the tire is reduced agreater amount of resistance will be introduced into the circuit therebyreducing the strength of the signal to the pressure gauge 14A.

It is thus seen that a continuous simple and foolproof monitoring systemhas been provided for monitoring the air pressure of front, rear andspare tires on any vehicle. Additionally. wheel bearing problems in thewheels will be detected. The speed of the wheel rotation will not affectthe sensitivity of the monitoring system. The signalling indicators maybe either on or off lights or pressure gauges to give precise readingsof the air pressure in the tires. The signal indicators may be testedeach time the vehicle ignition key is moved to the start position toverify that the lights or gauges are operative. The air pressuremonitoring system may be used on existing cars with few chanGes in theexisting structure being required or may be incorporated into vehiclesat the plant. The electrical connections in both the front and rearwheels are enclosed and protected from dust and moisture and should benearly maintenance free. The system of this invention is equally adaptedfor use on vehicles having either brake shoes or disc brakes.

I claim:

l. A tire pressure and wheel bearing monitoring system comprising,

a vehicle having front and rear wheels and tires,

a vehicle front wheel air pressure signalling unit on said front wheelrotatable therewith and in communication with the interior of saidvehicle front tire,

a stationary front axle having a rotatable wheel hub mounted thereon, anouter end portion of said axle being exposed outwardly of said wheelhub, an enclosure cover carried on said hub and extending over saidouter end portion,

an insulated electrical contact axially recessed in said outer end ofsaid axle and an electrically conductive spring positioned in andinsulated from said cover and frictionally and yieldably engaging saidcontact, said spring being operatively connected to said signallingunit,

an indicator electrically connected to said air pressure signalling unitin an electrical circuit including an electrical power supply, saidcontact and said spring whereby variations in the front tire airpressure are indicated on said indicator, and

said spring being positioned closely adjacent said outer end of saidaxle such that upon said electrical contact in said outer end of saidaxle and said conductive spring becoming disaligned said conductivespring will electrically contact said outer end of said axle and saidcontact and said indicator will be activated by a circuit beingestablished through said axle, contact and spring.

2. The structure of claim 1 wherein said air pressure signalling unit ispositioned with its longitudinal axis parallel to the axis of rotationof said front wheel thereby being unaffected by centrifugal forces assaid front tire is rotated.

3. The structure of claim 1 wherein said contact on said outer end ofsaid axle is further defined as being connected to an insulated wireextending through an axial bore in said axle.

4. The structure of claim I wherein said air pressure signalling unitincludes a variable electrical resistance responsive to a diaphragmexposed to the air pressure of said front tire.

5 S. The structure of claim 4 wherein said indicator unit iselectrically responsive to the voltage across it and is connected inseries to said si allin unit.

6. The structure of claim 5 w erein said indicator is further defined asbeing in a second circuit including said electrical power source and anignition switch, said ignition switch having one position for closingsaid second circuit through said indicator.

7. A tire pressure and wheel bearing monitoring system comprising,

a vehicle having from and rear wheels and tires,

8. vehicle rear wheel air pressure signalling unit on said rear wheelrotatable therewith and in communication with the interior of said reartire,

a rotatable rear axle having a housing, said wheel and tire mounted onsaid axle and adapted to turn therewith,

an electrically conductive ring on said axle rotatable therewith andinsulated therefrom by insulation means,

a stationary brush in a brush holder on said housing frictionally andyieldably engaging the top exterior of said ring, said ring beingoperatively connected to said signalling unit,

an indicator electrically connected to said air pressure signalling unitin an electrical circuit including an electrical power supply, said ringand said brush whereby variations in the rear tire air pressure areindicated on said indicator, and

said brush holder being closely spaced to the exterior of said ring suchthat upon said rear axle moving closer to the top of said housing, saidring will electrically engage said brush holder and said indicator willbe activated by a circuit being established through said housing, brushholder and brush.

8. The structure of claim 7 wherein said air pressure signalling unit ispositioned with its longitudinal axis parallel to the axis of rotationof said rear wheel thereby being unaffected by centrifugal forces assaid rear tire is rotated.

9. The structure of claim 1 and a vehicle rear wheel air pressuresignalling unit on said rear wheel rotatable therewith and incommunication with the interior of said rear tire, a rotatable rear axlehaving a housing, said wheel and tire mounted on said axle and adaptedto turn therewith, an electrically con ductive ring on said axlerotatable therewith and insulated therefrom by insulation means, astationary brush in a brush holder on said housing frictionally andyieldably engaging the top exterior of said ring, said ring beingoperatively connected to said signalling unit, and a second indicatorelectrically connected to said air pressure signalling unit in anelectrical circuit including an electrical power supply, said ring andsaid brush whereby variations in the rear tire air pressure areindicated on said second indicator, and said brush holder being closelyspaced to the exterior of said ring such that upon said rear axle movingcloser to the top of said housing said ring will electrically engagesaid brush holder and said second indicator will be activated by acircuit being established through said housing, brush holders and brush.

10. The structure of claim 9 wherein said air pressure signalling unitsare oriented in such a manner parallel to the axis of rotation of theassociated wheel that centrifugal forces generated during rotation ofsaid wheels do not afiect the operation of said signalling units.

f t It l =l

1. A tire pressure and wheel bearing monitoring system comprising, a vehicle having front and rear wheels and tires, a vehicle front wheel air pressure signalling unit on said front wheel rotatable therewith and in communication with the interior of said vehicle front tire, a stationary front axle hAving a rotatable wheel hub mounted thereon, an outer end portion of said axle being exposed outwardly of said wheel hub, an enelosure cover carried on said hub and extending over said outer end portion, an insulated electrical contact axially recessed in said outer end of said axle and an electrically conductive spring positioned in and insulated from said cover and frictionally and yieldably engaging said contact, said spring being operatively connected to said signalling unit, an indicator electrically connected to said air pressure signalling unit in an electrical circuit including an electrical power supply, said contact and said spring whereby variations in the front tire air pressure are indicated on said indicator, and said spring being positioned closely adjacent said outer end of said axle such that upon said electrical contact in said outer end of said axle and said conductive spring becoming disaligned said conductive spring will electrically contact said outer end of said axle and said contact and said indicator will be activated by a circuit being established through said axle, contact and spring.
 2. The structure of claim 1 wherein said air pressure signalling unit is positioned with its longitudinal axis parallel to the axis of rotation of said front wheel thereby being unaffected by centrifugal forces as said front tire is rotated.
 3. The structure of claim 1 wherein said contact on said outer end of said axle is further defined as being connected to an insulated wire extending through an axial bore in said axle.
 4. The structure of claim 1 wherein said air pressure signalling unit includes a variable electrical resistance responsive to a diaphragm exposed to the air pressure of said front tire.
 5. The structure of claim 4 wherein said indicator unit is electrically responsive to the voltage across it and is connected in series to said signalling unit.
 6. The structure of claim 5 wherein said indicator is further defined as being in a second circuit including said electrical power source and an ignition switch, said ignition switch having one position for closing said second circuit through said indicator.
 7. A tire pressure and wheel bearing monitoring system comprising, a vehicle having front and rear wheels and tires, a vehicle rear wheel air pressure signalling unit on said rear wheel rotatable therewith and in communication with the interior of said rear tire, a rotatable rear axle having a housing, said wheel and tire mounted on said axle and adapted to turn therewith, an electrically conductive ring on said axle rotatable therewith and insulated therefrom by insulation means, a stationary brush in a brush holder on said housing frictionally and yieldably engaging the top exterior of said ring, said ring being operatively connected to said signalling unit, an indicator electrically connected to said air pressure signalling unit in an electrical circuit including an electrical power supply, said ring and said brush whereby variations in the rear tire air pressure are indicated on said indicator, and said brush holder being closely spaced to the exterior of said ring such that upon said rear axle moving closer to the top of said housing, said ring will electrically engage said brush holder and said indicator will be activated by a circuit being established through said housing, brush holder and brush.
 8. The structure of claim 7 wherein said air pressure signalling unit is positioned with its longitudinal axis parallel to the axis of rotation of said rear wheel thereby being unaffected by centrifugal forces as said rear tire is rotated.
 9. The structure of claim 1 and a vehicle rear wheel air pressure signalling unit on said rear wheel rotatable therewith and in communication with the interior of said rear tire, a rotatable rear axle having a housing, said wheel and tire mounted on said axle and adapted to turn therewith, an electrically conductive ring on said axle rotAtable therewith and insulated therefrom by insulation means, a stationary brush in a brush holder on said housing frictionally and yieldably engaging the top exterior of said ring, said ring being operatively connected to said signalling unit, and a second indicator electrically connected to said air pressure signalling unit in an electrical circuit including an electrical power supply, said ring and said brush whereby variations in the rear tire air pressure are indicated on said second indicator, and said brush holder being closely spaced to the exterior of said ring such that upon said rear axle moving closer to the top of said housing said ring will electrically engage said brush holder and said second indicator will be activated by a circuit being established through said housing, brush holders and brush.
 10. The structure of claim 9 wherein said air pressure signalling units are oriented in such a manner parallel to the axis of rotation of the associated wheel that centrifugal forces generated during rotation of said wheels do not affect the operation of said signalling units. 